NATもちゃんとかいとけ
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ip route 0.0.0.0 0.0.0.0 bri0 per

int BRI0

ip addr negotiated
encap ppp
no keepalive
dialer string **********
dialer-group 1
isdn switch-type ntt
ppp auth pap callin
ppp pap sent-username ****** password 0 *************

dialer-list 1 prtcol ip permit